package com.decoration.basic.util;

//import java.security.SecureRandom;
import java.util.UUID;


/**
 * 生成序列id工具，分为时间戳id和uuid
 */
public class SnowFlake {

    /**
     * 起始的时间戳
     */
    private final static long START_STMP = 1480166465631L;

    /**
     * 每一部分占用的位数
     */
    private final static long SEQUENCE_BIT = 12; //序列号占用的位数
    private final static long MACHINE_BIT = 5;   //机器标识占用的位数
    private final static long DATACENTER_BIT = 5;//数据中心占用的位数

    /**
     * 每一部分的最大值
     */
    private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
    private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);

    /**
     * 每一部分向左的位移
     */
    private final static long MACHINE_LEFT = SEQUENCE_BIT;
    private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
    private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;

    private long datacenterId;  //数据中心
    private long machineId;     //机器标识
    private long sequence = 0L; //序列号
    private long lastStmp = -1L;//上一次时间戳

    public SnowFlake(long datacenterId, long machineId) {
        if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
            throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0");
        }
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
        }
        this.datacenterId = datacenterId;
        this.machineId = machineId;
    }

    /**
     * 产生下一个时间戳ID
     *
     * @return
     */
    public synchronized long nextId() {
        long currStmp = getNewstmp();
        if (currStmp < lastStmp) {
            throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
        }

        if (currStmp == lastStmp) {
            //相同毫秒内，序列号自增
            sequence = (sequence + 1) & MAX_SEQUENCE;
            //同一毫秒的序列数已经达到最大
            if (sequence == 0L) {
                currStmp = getNextMill();
            }
        } else {
            //不同毫秒内，序列号置为0
            sequence = 0L;
        }

        lastStmp = currStmp;

        return (currStmp - START_STMP) << TIMESTMP_LEFT //时间戳部分
                | datacenterId << DATACENTER_LEFT       //数据中心部分
                | machineId << MACHINE_LEFT             //机器标识部分
                | sequence;                             //序列号部分
    }

    private synchronized long getNextMill() {
        long mill = getNewstmp();
        while (mill <= lastStmp) {
            mill = getNewstmp();
        }
        return mill;
    }

    private long getNewstmp() {
        return System.currentTimeMillis();
    }

    //获取新的uuid
    public String getNewUuid(){
        return UUID.randomUUID().toString().replaceAll("-", "");
    }

    private static SnowFlake instance;

    public static SnowFlake getInstance() {
        if (instance == null) {
            synchronized (SnowFlake.class) {
                if (instance == null) {
                    instance = new SnowFlake(2, 3);
                    /*try {
                        SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
                        instance.dataCenterId = random.nextInt((int) instance.maxDataCenterId);
                        instance.workerId =random.nextInt((int) instance.maxWorkerId);
                        try {
                            InetAddress addr = inetAddress.getLocalHost();

                            instance.workerId = Hashing.crc32().hashBytes(addr.getHostName().getBytes()).padToLong() % instance.maxWorkerId;
                        } catch (UnknowHostException ex){
                            log.error("获取主机名失败: ",ex);
                        }
                        if (instance.dataCenterId > instance.maxDataCenterId){
                            throw new IllegalArgumentException(String.format("data center Id can't be greater than %d",instance.maxDataCenterId));
                        }
                        if (instance.workerId > instance.maxWorkerId){
                            throw new IllegalArgumentException(String.format("worker  Id can't be greater than %d",instance.maxDataCenterId));
                        }
                    } catch (Exception e){
                        log.error("init collector id fail: ",e);
                    }*/
                }
            }
        }
        return instance;
    }
    /*public static void main(String[] args) {
        SnowFlake snowFlake = new SnowFlake(2, 3);

        for (int i = 0; i < (1 << 12); i++) {
            System.out.println(snowFlake.nextId());
            System.out.println(snowFlake.getNewUuid());
        }
    }*/
}